Electrical circuit for providing automatic alternate switching

ABSTRACT

Alternate switching between two parallel circuits is accomplished by the use of a relay and an incandescent lamp in each circuit. Each circuit is routed through the energization coil of its own relay and the contact and off terminal of the relay in the other circuit to prevent simultaneous closure of both circuits. Increased resistance in the circuit in use due to temperature rise in the incandescent lamp causes the other circuit to close following any interruption of the current supply. Appropriate intermittent breaking of the supply circuit effects automatic alternate flip-flop type switching between circuits.

United States Patent [191 Friedman ELECTRICAL CIRCUIT FOR PROVIDING AUTOMATIC ALTERNATE SWITCHING Inventor: Jerome D. Friedman, 210 Summer St., Som erville, Mass. 02144 Filed: May 21, 1973 Appl. No; 362,024

[56] References Cited UNITED STATES PATENTS 3,0 65379 11/1962 Cade ..315/322 v Primary Examiner-Herman .l. Hohauser- Attorney, Agent, or Firm-Harry A. Herbert, Jr; Willard R. Matthews, Jr.

[ 5] June 4, 1974 [57] ABSTRACT Alternate switching between two parallel circuits is accomplished by the use of a relay and an incandescent lamp in each circuit. Each circuit is routed through the energization coil of its own relay and the contact and off terminal of the relay in the other circuit to prevent simultaneous closure of both circuits. Increased resistance in the circuit in use due to temperature rise in the incandescent lamp causes the other circuit to close following any interruption of the current supply. Appropriate intermittent breaking of the supply circuit effects automatic alternate flip-flop type switching between circuits.

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I6 14- FLA E-- 1 ELECTRICAL CIRCUIT FOR PROVIDING AUTOMATIC ALTERNATE SWITCHING BACKGROUND OF THE INVENTION This invention relates to switching circuits and in particular to alternate switching and flip-flop type devices.

.There currently exists various industrial and academic applications ,in which relatively low speed alternate switching of high currents is required. The alternate switching required in a Foucoult pendulum electromagnet is an example of such an industrial use. In the field of education it would be desirable to utilize such an alternate switching circuit to demonstrate the principle of flip-flop type devices. Although certain currently available switching schemes can be used for these purposes there remains a need for simpler, more inexpensive means for accomplishing the same ends. The present invention is directed toward providing such a simple, inexpensive alternate switching device.

SUMMARY OF THE INVENTION The alternate switching device of the invention has two parallel electrical circuits between its input and output. Each circuit includes an incandescent lamp and a relay. Each circuit is routed through the off contact of the relay of theother circuit to provide mutually ex clusive on operation. The circuits have substantially equal initial impedance. Alternate operation between circuits is achieved through the impedance changes resulting from the alternate heating and cooling of the lamps.

It is a principal object of the invention to provide a new and improved alternate switching device.

It is another object of the invention to provide an inexpensive electrical circuit of simple construction that can be utilized for alternate switching of high currents.

DESCRIPTION OF DRAWING The sole FIGURE of the drawing is a schematic diagram of the alternate switching circuit of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the sole FIGURE of the drawing, the invention is illustrated essentially by alternate switching network I. Switching network I comprises input terminal 14, output terminal 15, relays I8 and 19, and incandescent lamps and 11. It is arranged in two parallel circuits. A first circuit can be traced from input terminal 14 to off terminal 7 and current carrying contact 9 of relay 19, through energization coil 2 of relay 18, through incandescent lamp 10 and finally to output terminal 15. The other circuit also begins at input terminal 14 and is routed through off terminal 5 and current carrying contact 8 of relay 18, the energization coil 3 of relay l9, and incandescent lamp 1]. It terminates at output terminal 15. Circuit breaking devices 12 and 13 are provided for reset purposes. The alternate switching networks can be operated by rounding output terminal 15, and intermittently applying an electrical current from current source 17 to input terminal 14. Although illustrated as a battery, current source l4 can be any appropriate source of electrical current, either AC or DC. Intermittent operation is accomplished by means of switch 16. Manual switch 16 can, of course, be replaced by any suitable automatic switching device. Incandescent lamps l0 and I 11 and relays l8 and 19 are selected to have substantially equal impedance values. In operation, current flowing through one lamp will cause its temperature to rise and hence increase its resistance. Any momentary interruption in the supply current source will make the switching network automatically select the other circuit when the supply current is reapplied. The lamp in the second circuit then becomes heated (with a concommitant increase in resistance) while the lamp in the originally energized circuit cools off. Because of the shift in impedance values of the respective circuits resulting from the increasing and decreasing resistance values of the lamps, the next current source interruption will switch the alternate switching network back to the originally energized circuit. Automatic alternate switching of the switching network will therefore result from continued intermittent switching of the current supply. It is, of course, necessary to time the switching of the current supply to permit sufficient heating and cooling of the lamps. That is, on times must be long enough to effect an appreciable impedance difference between switching circuits.

While the invention has been described in its preferred embodiment, it is understood that the words which have been'used are words of description rather than words of limitation and that changes within the purview of the appended claims may be made without departing from the scope and spirit of the invention in its broader aspects.

What is claimed is:

1. An electrical circuit for providing automatic alternate switching comprising an input,

an output,

first and second substantially identical incandescent lamps, I first and second relays, each relay comprising an energization coil and a current carrying contact having on and off terminals, the off terminals of each relay being connected directly to each other and to said input, said first lamp, the energization coil of said first relay, the current carrying contact of said second relay and its off terminal being connected in series between the input and output, and,

said second lamp, the energization coil of said second relay, the current carrying contact of said first relay and its off terminal being connected in series between the input and output,

a source of electrical current connected between said input and ground, means for intermittently disconnecting said source of electrical current, and

means connecting said output to ground. 

1. An electrical circuit for providing automatic alternate switching comprising an input, an output, first and second substantially identical incandescent lamps, first and second relays, each relay comprising an energization coil and a current carrying contact having on and off terminals, the off terminals of each relay being connected directly to each other and to said input, said first lamp, the energization coil of said first relay, the current carrying contact of said second relay and its off terminal being connected in series between the input and output, and, said second lamp, the energization coil of said second relay, the current carrying contact of said first relay and its off terminal being connected in series between the input and output, a source of electrical current connected between said input and ground, means for intermittently disconnecting said source of electrical current, and means connecting said output to ground. 